Inter-wall foamed thermal insulation



May 27, 1969 R. R. POOLE 3,446,881

INTER-WALL FOAMED THERMAL INSULATION Filed March 9. 1966 United States Patent 3,446,881 INTER-WALL FOAMED THERMAL INSULATION Ronald Robertson Poole, Berkhamsted, England, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Mar. 9, 1966, Ser. No. 532,958 Claims priority, application Great Britain, Apr. 1, 1965, 13,775/65 Int. Cl. B32b 1/02, 31/06; B29d 27/00 U.S. Cl. 264-45 4 Claims ABSTRACT OF THE DISCLOSURE In the preferred form the inner liner member and the outer shell member of a refrigerator cabinet have applied to their juxtaposed spaced surfaces continuous substantially parallel flexible strips projecting inwardly about two-thirds the width of the space between said members and arranged alternately. The remaining space between the members is substantially filled with a polyurethane foam containing fluorinated hydrocarbon gas.

This invention relates to inter-wall foamed thermal insulation, and particularly to a method of making structures incorporating the same.

Such foaming is effected by pouring, or injecting, or flooding into the space between the walls a mixture of reactants which, by the evolution of a gas, produce a cellular structure. This structure, formed of closed cells containing entrapped gas, is not only an effective insulator but constitutes a reinforcement of the whole assembly.

Such a method can be applied to refrigerator cabinets, boxes and the like, and to the walls and partitions of buildings, boats and like structures.

The foamed cellular insulation can be polystyrene, polypropylene, polyurethane or similar materials; and the evolved gas and the reactants are preferably such as to produce a cellular structure whose closed cells contain a gas of low thermal conductivity.

The foaming is in most cases an exothermic reaction; and consequently, as the elements of the assembly cool, stresses are set up which are liable to cause cracks. Furthermore there is the risk and likelihood that the bond between the rigid insulation and the retaining walls will be loosened or even broken completely.

These deleterious effects are avoided by means of this invention, according to which the inter-wall cavity within which the insulation is foamed and cast is fittted with spaced compressible flexible members which form expansion joints.

Thus, as the foam sets and the whole assembly cools, any stresses which otherwise would be set up are relieved. This stress-relief is effective throughout the life of the assembly.

The scope of the monopoly is defined by the appended claims; and how the invention may be performed is hereinafter particularly described with reference to the accompanying drawings, in which:

FIGURES l and 2 are diagrammatic cross-sections on lines II and 11-11 respectively to illustrate the method as applied to a household refrigerator cabinet;

FIGURE 3 is a somewhat diagrammatic and broken perspective view of such a cabinet ready to be insulated; and

FIGURES 4 and 5 are cross-sections of two constructions of strips which act as expansion joints.

The refrigerator cabinet shown in the drawings is of conventional form, having walls in the form of an inner liner 1 and an outer shell 2, with a cavity therebetween which is filled or fitted with insulation. No door is shown;

nor are any shelves, fitments and equipment shown, as they all can be of conventional form.

In performing the invention, strips 3 are attached either to the outer surface of the inner liner 1 or to the inner surface of the outer shell 2; or, as shown, to both juxtaposed surfaces and spaced alternately.

These strips 3 divided the cavity into separate but intercommunicating compartments, as shown in FIGURE 3. With the cabinet in its upstanding position shown, the strips 3 are horizontal and project inwardly for a distance of about twothirds of the width of the inter-wall cavity.

The strips, as previously indicated, are compressible and flexible: thus they can be made of solid rubbery or like material, or of foamed rubber or like matter with an impervious coating. These are essentially stress-relieving members.

FIGURE 4 is a cross-section of a solid rubber strip 3 fixed to one of the cabinet walls as shown in FIGURE 3.

An alternative hollow strip, of triangular cross-section is shown in FIGURE 5.

In performing the invention, as applied to the refrigerator cabinet as shown diagrammatically in FIGURE 3, the cabinet is positioned front downwards as shown in FIG- URE 1. Through an aperture in the back of the cabinet liner (the top, in the position shown) a nozzle 4 is inserted, the nozzle being connected to a pipe 5 through a valve control device 6. The other end of the pipe is connected to a pump (not shown) which delivers the mixture of foam material from a tank (not shown). Such equipment is now conventional so it is not thought necessary to describe it in detail.

As insulation foam material, it is preferred to use a polyurethane made from a mixture of a polyisocyanate, such as a diisocyanate, and a polyhydroxy compound, such as a polyether, and an inert liquid fluorinated hydrocarbon which is vaporised during the reaction. Such materials and mixtures are well known, as previously indicated, as constituents to make rigid and semi-rigid foam insulation.

The cavity between the inner liner 1 and the outer shell 2, at the back of the cabinet and adjacent the aperture for the nozzle 4, is constituted by a header 7 forming a distribution chamber for the liquid mixture injected through the nozzle 4. By this there is a reasonably even distribution of the mixture first along the horizontally disposed channels and then down the vertically disposed channels (FIGURE 1) formed by the strips 3. As the mixture falls to the bottom of the down-turned cabinet assembly, the exothermic reaction begins and the foam boils and bubbles upwardly. By virtue of the intercommunication between the compartments formed by the strips, the whole of the space is filled as the mixture completes its expansion into a foam.

This method and the resultant structure is of particular utility if one or both of the members and the liner and the shell are made of a plastics material, so that a firm bond is made with the foamed insulation.

I claim:

1. A method of making an inter-wall insulated structure, in which the improvement comprises fitting on one of the juxtaposed surfaces of one of the walls spaced compressible flexible members of such limited dimensions relative to said one surface so as to project inwardly about two-thirds of the width of the inter-wall cavity, and then introducing a polyurethane foam forming reactant mixture into the cavity to produce an insulation foam.

2. A method of making an inter-wall insulated structure, in which the improvement comprises fitting on the juxtaposed surfaces of the walls spaced continuous substantially parallel compressible flexible members of such limited dimensions relative to such surfaces so as to project alternately inwardly less than the distance between the juxtaposed surfaces to form intercommunicating compartments in the inter-wall cavity, and then introducing a polyurethane foam forming reactant mixture into the cavity to produce an insulation foam throughout said compartments.

3. A method of making a refrigerator cabinet having an inner liner member and an outer shell member in which the impromevent comprises fitting to one of the Walls of one of the members a plurality of continuous substantially parallel flexible strips extending substantially the entire distance between the edges along said one wall, interfitting said members so that said strips form a plurality of intercommunicating compartments within the inter-wall cavity, said strips projecting from said one wall less than the distance between said members, and introducing a polyurethane reactant mixture of foam insulation material into said cavity so as to substantially fill the same with foam.

4. A method of making a refrigerator cabinet according to claim 11 in which said flexible strips are hollow.

References Cited UNITED STATES PATENTS 3,013,922 12/1961 Fisher 264-45 JULIUS FROME, Primary Examiner.

LEON GARRETT, Assistant Examiner.

US. Cl. X.R. 

